P0C32: battery cooling performance depends on inlet temperature

P0C32 is the battery cooling-system performance monitor in GM's hybrid document. The criterion is not one fixed module temperature for every ambient condition. The controller compares maximum battery-module temperature with a limit that changes according to inlet temperature.

Use the inlet-dependent threshold

The source's calibration table gives, for example, a 52°C module limit at a 20°C inlet and a 61°C limit at a 40°C inlet. These are examples from this monitor, not universal service specifications. A module-temperature reading without the simultaneous inlet condition cannot reproduce the test's decision.

GM requires 1,200 failures out of 1,200 samples at a 100 ms interval. This prolonged condition differs from a brief high reading and from the separate fan electrical-feedback faults in the surrounding rows.

Establish that the temperatures are valid

Maximum module temperature must be considered valid; the source defines that condition using the number of active module-temperature circuit faults. Listed inlet-temperature faults and P0A1F also inhibit evaluation, and the low-voltage supply must satisfy its specified window.

Preserve inlet temperature, maximum module temperature, related circuit faults and the operating history. The code does not identify a failed fan or mandate replacing the battery. A qualified hybrid technician must use the applicable vehicle procedure to establish the cooling cause and verify sustained normal behavior. High-voltage battery access requires the proper service precautions.

Source and applicability

GM 2010 10OBDG10 Hybrid Diagnostics, cited BPCM or hybrid-controller monitor only. Historical calibration values are not universal specifications; no per-code model, engine or hardware fitment has been established. GM PDF, physical page 240.